Many wireless telecommunications systems, i.e. cellular communications networks, are divided into a series of cells that provide coverage for a particular service area. Each cell is contains a base station, which communicates with mobile subscriber users on an operating frequency set comprising a plurality of radio channels. Each channel represents an information signal at a particular frequency. In order to improve the usage efficiency of the channel, many coding schemes and networks divide the channel slot (or band) into multiple sub-channels (subcarriers), allowing for more subscribers to operate in the same bandwidth. Motorola's iDEN (integrated Digital Enhanced Network) is an example of this type of system.
However, a multiple carrier Wideband integrated Digital Enhanced Network (WiDEN) signal suffers from poor peak-to-average power ratio (PAR) due to the signal being composed of two to four combined 25 kHz iDEN slot formats, each separated by 25 kHz. The sync and pilot symbols occur at the same symbol times and phases in both subcarriers. This is desirable for maintaining compatibility with the current iDEN slot format, but contributes to poor PAR.
Peak to average ratio compression is a technique for improving average power levels from an amplifier with limited peak power capability. However, the additive nature of having the sync and pilot symbols occur simultaneously in both subcarriers creates large peak power levels, thereby reducing the overall effective output power level of the transmitter. Typical methods of lowering PAR, such as adaptive gain control and hard or soft clipping, create splatter, which impacts adjacent channel power specs and may raise the noise floor of the transmitted signal.